Humm is one of 29 Maryland athletes competing in the four-day event in Michigan. He's a three-time transplant recipient.

"My first heart transplant was when I was 16-years-old in high school," Humm said.

Humm had to have a second heart transplant 11 years later, and then his kidneys failed.

"Back in 2002, I developed kidney failure due to medication, so I received a gift from my sister. Debbie donated her kidney to me, and I'll be forever grateful," Humm said.

This is Humm's third trip to the games, where he'll compete in a several events, including a 100- and 200-meter sprint and tennis.

"It's great competition, but not only that, to hear the other amazing stories of transplant recipients, to see how well everybody else is doing, and more importantly, it's not about medaling. It's about seeing how everybody is doing," Humm said.

In Maryland, there 2,000 people on the waiting list, and that number is over 115,000 nationwide, and that's why Stacey Thompson, from the Living Legacy of Maryland, said donation is so important.

"Share it with your family. Let them know your decision. It's so important for people to become registered because this is such an important cause. We have so many people on the waiting list right now," Thompson said.

"I wouldn't be here without organ donation," Humm said.

That is something his wife thinks about every day. She said the Transplant Games are quite emotional.

"Without a doubt, this is the third games, and I will cry at some point just from saying hello to somebody because that was their loved one's final decision," Angela Humm said.

The games start on Sunday, and 3,000 transplant recipients from around the country will compete in much the same way the Olympic athletes will in London.

"To be going along coinciding with the Olympics is a pretty neat feeling," Humm said.